Smoke Production Research Articles

Preparation of P/N/Si‐containing covalent organic framework‐based flame retardants and their application in epoxy resins

AbstractBalancing the enhancement of flame retardancy of epoxy resin while maintaining its mechanical capacities intact poses a significant challenge in the realm of flame‐retardant epoxy resins. To reach the above objectives, a COF‐based synergistic flame retardant with phosphorus, nitrogen, and silicon (PA‐COF@MT) was synthesized using phytic acid (PA), montmorillonite (MT), and covalent organic framework (COF). When PA‐COF@MT was added at 4 wt%, EP/PA‐COF@MT exhibited a reduction of 42.1% in peak heat release rate (PHRR), 45.84% in total heat release (THR), and 59.8% in total smoke production (TSP) compared with the pure EP. LOI increased by 30.5% and UL‐94 tested to V‐0 grade. flame‐retardant index (FRI) value of 3.03, achieving a “good” rating. Fire growth indices and mean effective combustion heat were increased while mechanical properties also improved. These findings suggest that the flame retarding mechanism of PA‐COF@MT is mainly through vapor phase and condensed phase actions. The combined effects of phosphorus, nitrogen, and silicon make the surface of carbon residue solid and dense, resulting in excellent heat insulation and smoke suppression effects. In simple terms, this study provides new insights into COF‐based flame retardants. Combining low‐cost and simple preparation methods, PA‐COF@MT has broad application prospects in flame‐retardant epoxy resin systems.

Fabrication of CoFe‐layered double hydroxide for flame retardant and smoke suppression of silicone rubber foam

AbstractIn order to improve the flame retardancy and smoke suppression of silicone rubber foam (SRF), the CoFe‐LDH was fabricated by coprecipitation method and used as flame‐retardant ingredient in SRF. The influence of CoFe‐LDH on the flame retardancy, combustion behavior, and thermal stability of SRF was investigated. The results demonstrate that SRF containing only 1.0 phr CoFe‐LDH can pass V‐0 rating in the vertical combustion test, with a limiting oxygen index of 28.6%. The total heat release and total smoke production are 22.2% and 61.1% lower than that of SRF, respectively. Moreover, CoFe‐LDH can improve the thermal stability of SRF in the high temperature range, and the char residue at 900°C of SRF/LDH composite is obviously higher than that of pure SRF. In addition, to further understand the flame‐retardant mechanism of CoFe‐LDH, the micromorphology of the char residue and the gaseous products during heating for SRF and SRF/LDH composite were analyzed. The results indicate that CoFe‐LDH exhibits excellent flame‐retardant effects in both condensed and gaseous phases for its functions of catalysis, carbonization, and nonflammable gas release. This study provides a more efficient and convenient strategy for the flame retardant and smoke suppression research of SRF.

DOPO chemically modified mesoporous silica composites: Preparation, flame retardancy, and thermodynamic properties

AbstractOrganic flame retardant 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was used to decorate the pores of mesoporous silica (m‐SiO2) nanospheres to prepare a new composite flame retardant (DK‐SiO2). The content of DOPO in DK‐SiO2 is about 17 wt%. Due to the chemical bonding, DK‐SiO2 not only enhances the flame retardant performance, but also effectively avoids adverse effects of DOPO on the glass transition temperature and mechanical properties of epoxy resin (EP). At 9 wt% loading, the limiting oxygen index of the EP increased from 25.7 to 31.2, and successfully passed the UL‐94 V‐0 rating. Besides, DK‐SiO2 can significantly reduce the peak heat release rate, total heat release, and total smoke production of EP, with reductions of 26%, 32%, and 20.8%, respectively. Compared with the simple blended sample, DK‐SiO2 not only has better flame retardant performance but also shows significant advantages in thermodynamic properties. The glass transition temperature, impact, and tensile strength, as well as storage and flexural modulus have been improved. This excellent flame retardant performance is mainly attributed to the gas‐condensed synergistic flame retardant mechanism between DOPO and m‐SiO2. The good thermodynamic performance is due to the excellent dispersion of DK‐SiO2 nanospheres in the EP.

Fabrication of Flame-Retardant Ammonium Polyphosphate Modified Phytic Acid-Based Rigid Polyurethane Foam with Enhanced Mechanical Properties.

Ammonium polyphosphate (APP) and self-made nickel phytate (PANi) were used as modified materials to prepare green biomass rigid polyurethane foam (RPUF). The flame retardancy, thermal stability, smoke toxicity and mechanical properties of the modified RPUF were investigated by limiting oxygen index (LOI), a cone calorimetry (CONE) test, thermogravimetric analysis and a compression test. The results showed that the RPUF with 10 wt% APP (PANi/APP10) had the highest LOI of 26.5%. Its peak heat release rate (PHRR) and total heat release (THR) were reduced by 29.64% and 24.05% compared with PANi/APP0 without APP. And its smoke production rate (SPR) and total smoke release (TSR) decreased by 33.14% and 19.88%, respectively. Compared with pure RPUF, the compressive strength of PANi/APP10 was increased by 50%, mainly because APP itself was an ultra-fine powder, which was better compatible with the matrix and improved the hardness of the material. The results showed that the synergistic effect of the gas phase and the condensed phase mechanism could effectively improve the flame-retardant effect. The current research results provided a new strategy for the preparation of green and low-toxicity RPUF.

In utero nicotine exposure affects murine palate development.

Despite data linking smoking to increased risk of fetal morbidity and mortality, 11% of pregnant women continue to smoke or use alternative nicotine products. Studies confirm that nicotine exposure during pregnancy increases the incidence of birth defects; however, little research has focused on specific anatomic areas based on timing of exposure. We aim to determine critical in utero and postnatal periods of nicotine exposure that affect craniofacial development, specifically palate growth. Malformation of the palatal structures can result in numerous complications including facial growth disturbance, or impeding airway function. We hypothesized that both in utero and postnatal nicotine exposure will alter palate development. We administered pregnant C57BL6 mice water supplemented with 100 μg/mL nicotine during early pregnancy, throughout pregnancy, during pregnancy and lactation, or lactation only. Postnatal day 15 pups underwent micro-computed tomography (μCT) analyses specific to the palate. Resultant pups revealed significant differences in body weight from lactation-only nicotine exposure, and μCT investigation revealed several dimensions affected by lactation-only nicotine exposure, including palate width, palate and cranial base lengths, and mid-palatal suture width. These results demonstrate the direct effects of nicotine on the developing palate beyond simple tobacco use. Nicotine exposure through tobacco alternatives, cessation methods, and electronic nicotine delivery systems (ENDS) may disrupt normal growth and development of the palate during development and the postnatal periods of breastfeeding. Due to the recent dramatic increase in the use of ENDS, future research will focus specifically on this nicotine delivery method.

Heat Transfer Analysis of Double Pipe Condenser on the Liquid Smoke Production of Cocoa Pod Husk Using Computational Fluid Dynamics

Heat Transfer Analysis of Double Pipe Condenser on the Liquid Smoke Production of Cocoa Pod Husk Using Computational Fluid Dynamics

Synergistic effect of coal gangue on intumescent flame retardants

Abstract In order to improve the flame retardant properties of wood plywood, intumescent flame retardant coatings were prepared using melamine, borate, pentaerythritol and urea as the basic formulations and gangue as a modified additive. The flame retardancy of the samples was characterized using a cone calorimeter, scanning electron microscope, X-ray diffraction and thermogravimetric analysis. In addition, the study investigated the effect of gangue content on the properties of the prepared coatings. The results show that the doping of gangue in intumescent flame retardant coatings can improve the flame retardant effect of the coatings. Specifically, when the mass fraction of gangue was 8 wt%, the exothermic rate, total smoke production and total exothermic amount of the coating were significantly reduced. Moreover, the addition of gangue promoted the formation of a continuous and dense carbon layer structure during the combustion process of the coating, which produced a molten substance that effectively isolated oxygen and heat, thus strengthening the fire-retardant and heat-insulating properties of the coating. The results of this study provide valuable insights into the development of flame retardant coating formulations for wood plywood.

Downstream strategies of liquid smoke products as a preservative and smoke aroma in fishery products

Smoked fish is a fishery product that meets the nutritional needs of the population. The traditional smoking method leads to the production of H2S, which reduces the aroma and is carcinogenic. The liquid smoke technology offers a solution to the challenges associated with the application of traditional smoking methods. However, the use of the liquid smoke method remains limited in smoked fish businesses. This study aimed to evaluate and develop a downstream strategy for producing and distributing liquid smoke to facilitate its implementation by smoked fish businesses based on SWOT analysis. This study employed a quantitative descriptive methodology utilizing the strengths, weaknesses, opportunities, and threats (SWOT) analytical framework. The data were collected through interviews and questionnaires. The obtained data were subjected to weight calculations using the Expert Choice tool. The research findings indicate that the optimal approach for developing downstream liquid smoke products is to create a novel product in the form of liquid smoked fish. Liquid-smoked fish are immersed in or coated with liquid smoke to achieve an extended shelf life and smoky aroma, without traditional smoking methods. In addition, it establishes a strategic alliance between scholars, entrepreneurs, and the government. Strategic relationships can be established by developing a shared agenda focusing on fostering a sustainable blue economy. The blue economy refers to the use of hygienic, healthy, and non-carcinogenic fishing products such as smoked fish to promote sustainable economic growth and enhance community welfare.

Electrostatic assembly of metal organic frameworks nanocubes on electrochemically exfoliated graphene nanoflakes: Superior role in flame retardance

The extensive usage of epoxy resin (EP) is facing the head-scratching challenge of high fire hazard. As such, the electrostatic assembly of metal organic frameworks (MOFs) nanocubes on electrochemically exfoliated graphene nanoflakes is performed to acquire the hybrid of PG@UIO. The corresponding role and behavior in flame retardance are explored in detail. By adding 2.0 wt% PG@UIO, the reductions in peak heat release rate, total heat release, peak smoke production rate, peak CO yield, peak CO2 yield reach 49.2 %, 44.3 %, 56.1 %, 57.7 % and 51.3 %. The in-situ volatiles analysis points out the reductions of 35.1 %, 29.4 %, 50.8 %, 32.5 % in the maximal intensities of aromatic compounds, ethers, CO and HCN. The mechanical interlocking area between PG@UIO nanostructures and EP molecular chains contributes to the enhanced mechanical performances. Specifically, by adding 2.0 wt% PG@UIO, the flexural strength is increased by 50.3 %. This work enables a new paradigm for fabricating fire-safe polymer composites with the judicious design of MOFs based flame retardant.

Optimizing calliandra (Calliandra calothyrsus) biomass pellets: Impact of particle size and bark composition

Calliandra biomass pellets offer a promising alternative energy source to replace fossil fuels. Typically, these pellets are produced by directly processing the stem and bark of the calliandra (Calliandra calothyrsus) plant without separation, aiming for manufacturing efficiency. This study investigated the quality differences between calliandra biomass pellets with and without bark and varying particle sizes. Particle sizes used were 20 mesh, 40 mesh, and 60 mesh. The pellets were made using a 12 mm diameter biomass pellet mold and a manual hydraulic press with a pressure of 3 tons. Characterization involved assessing proximate analysis, calorific value, physical and mechanical properties, and Fourier Transform Infrared analysis. The test results were compared with biomass pellet standards from Indonesia, Japan, Korea, and Germany. Results indicate that bark affects several properties, with higher ash content observed in pellets with bark due to the higher mineral content in bark. Volatile matter decreases with finer particle size, influencing combustion rate. Moisture content is higher in pellets with bark, impacting combustion efficiency and smoke production. Fixed carbon values are influenced by moisture and volatile matter content. Calorific values are generally higher in pellets without bark and smaller particle sizes. Density and compressive strength increase with decreasing particle size. FTIR analysis reveals differences in functional groups between pellets with and without bark, indicating variations in chemical composition. Overall, this research provides insight into the potential of calliandra biomass pellets with bark and without bark along with particle size as a renewable energy source.

Innovative Nanocomposite Coating for Aluminum Alloy in the Aircraft Manufacturing Industry with Increased Mechanical Strength, Flame Retardancy, and Corrosion Resistance

AbstractNanocomposites containing impermeable two‐dimensional materials are of significant interest for protecting metals against corrosion. Incorporating 4‐aminobutyltriethoxysilane (ABES) functionalized tantalum nitride (TaN) into a coating matrix enhances the barrier effect due to TaN's notable chemical and thermal stability. When integrated with graphitic carbon nitride (GCN) in polyurethane (PU), functionalized TaN significantly improves corrosion resistance and fire‐retardant capabilities. Electrochemical evaluations of aluminum coated with varying amounts of functionalized TaN/GCN in PU demonstrated substantial enhancements in protective behavior in chloride environments. The PU nanocomposite exhibited superior flame retardancy, with significant reductions in peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) compared to pure PU. Flame retardancy tests demonstrated increased thermal stability, attributed to the synergistic effects between GCN and silanized TaN. Electrochemical impedance spectroscopy (EIS) measurements showed a high coating resistance of 8.89×1011 Ω cm2 for PU/functionalized TaN/GCN, even after 40 days of electrolyte exposure. Additionally, the PU/functionalized TaN/GCN coating demonstrated exceptional water repellency, indicated by a water contact angle (WCA) of 164°. Mechanical tests revealed that PU/functionalized TaN/GCN exhibited favorable adhesion strength and hardness, maintaining integrity even under prolonged immersion. These findings suggest that this nanocomposite is a promising coating component for aerospace applications. The integration of functionalized TaN/GCN within the PU matrix presents a novel approach to developing multifunctional coatings with enhanced performance across various metrics essential for aerospace materials.

Fabrication of green montmorillonite modified bio-based rigid polyurethane foam with improved flame retardancy and enhanced mechanical properties

A low-carbon and sustainable green rigid polyurethane foam was prepared by compounding montmorillonite (MMT) with homemade barium phytate (BAPA). The flame retardancy, thermal stability and mechanical properties of the modified RPUFs investigated using the limiting oxygen index (LOI) method, cone calorimetry (CONE) and thermogravimetry. The results showed that the BAPA/MMT2 composite containing 2 wt% MMT had the highest LOI (25.1 %), and its peak heat release rate (PHRR) and total heat release (THR) were reduced by 14.33 % and 34.68 %, respectively, compared with that of the BAPA/MMT0 material without added MMT. In addition, the smoke production rate (SPR) and total smoke release (TSR) were reduced by 20.54 % and 30.77 %, respectively. BAPA/MMT2 had good flame retardancy and smoke suppression effect. The mechanical properties of BAPA/MMT2 with 2 wt% MMT were improved. The flame retardant mechanism confirmed that BAPA and MMT synergistically improved the quality of the carbon layer. At the same time, phosphorus-containing compounds (PO·), CO2 and water vapor were produced, which diluted the combustible gas in the gas phase and inhibit the flames spread. The current results provided a new strategy for the preparation of high-performance RPUFs.

Lignin-Based Carbon Fiber/Epoxy Resin Biocomposites with Excellent Fire Resistance and Mechanical Properties.

Carbon fiber (CF)-reinforced epoxy resin (EP) composites are lightweight materials with excellent comprehensive performance. However, the flammability of EP and the poor interfacial bonding between CF and EP are two key disadvantages that limit their further applications. Here, a kind of water-soluble lignin-based CF sizing agent (ELBEDK) is prepared through hydrophilic modification of enzymatic lignin, which can significantly enhance the interfacial interaction between CF and EP. Additionally, a highly efficient intumescent flame retardant (LMA) is prepared. The EP, enzymatic lignin, LMA and CF sized ELBEDK are compounded to obtain the fire-safety CF reinforced composites (SCF/FEP/L). The flame retardancy of SCF/FEP/L with 7% LMA (SCF/FEP7) reached V-0 rating. Moreover, SCF/FEP/L with 7% LMA and 15% lignin (SCF/FEP7/L15) present an limiting oxygen index (LOI)of 30.2% and V-0 of UL-94. Specifically, the total smoke production and the heat release rate are 47.8% and 46.81% lower than that of SCF/EP, respectively, indicating the improved smoke suppression and flame retardancy. The IFSS and flexural strength of SCF/FEP7/L15 are improved to be 59.4MPa and 511.1MPa, respectively. This study presents a simple approach to fabricate low-cost high performance lignin-based flame retardant CF/EP biocomposites with wide application potential.

Innovative multifunctional nanocomposite coated aluminum alloy for improved mechanical, flame retardant, and corrosion resistance in automobile industries

ABSTRACT Nanocomposites with impermeable two-dimensional materials show promise for metal corrosion protection. A coating matrix incorporating (3-aminopropyl)trimethoxysilane (AMS) functionalized molybdenum nitride (Mo2N) enhances the barrier effect due to its chemical and thermal stability. Further improvement is achieved by adding functionalized Mo2N into graphitic carbon nitride (GCN) within a polyurethane (PU) matrix, enhancing corrosion protection and fire retardancy. Electrochemical techniques evaluated the efficacy of aluminium coated with PU and varying concentrations of functionalized Mo2N/GCN. The resulting PU composite exhibited superior flame retardant capabilities, reducing peak heat release rate (pHRR), total heat release (THR), and total smoke production (TSP) compared to pure PU. Electrochemical impedance spectroscopy (EIS) showed enhanced coating resistance (5.55 × 101 1 Ω.cm2) even after 500 hours of exposure. Additionally, the composite displayed exceptional water repellency with a water contact angle (WCA) of 156° and commendable mechanical properties, including an adhesive strength of 19.2 MPa within the PU substrate. This multifunctional PU composite, incorporating functionalized Mo2N/GCN, presents a promising option for automotive coatings, offering corrosion protection, flame retardancy, water repellency, and mechanical robustness, thus enhancing durability and performance in harsh conditions.

Interpenetrated Multinetwork Hybrid Aerogels by Layered Montmorillonite and One-Dimensional Hydroxyapatite Fibers for Heat and Fire Insulation.

It is of practical significance to develop aerogels with effective thermal insulation characteristics together with fireproof properties as well as high mechanical strength. Here, an interpenetrated multinetwork hybrid aerogel realizing thermal insulation, flame retardancy, and high compression modulus is demonstrated. Specifically, one-dimensional hydroxyapatite nanowires (HAP) played dual roles as the aerogel support skeleton to entangle with layered montmorillonite (MMT) each other to form a three-dimensional interpenetrated multinetwork structure and to optimize the thermal conductivity by adjusting the pore space in current HAP/MMT/PVA hybrid aerogels. Therefore, the interpenetrated multinetwork hybrid aerogels exhibit superior thermal insulation performance in room temperature (0.033 W m-1 K-1, 298 K, air conditions) and largely enhanced ultrahigh compression modulus (80 MPa). Moreover, the obtained hybrid aerogels also exhibit excellent flame retardancy and self-extinguishing smoke suppression properties (peak heat release rate and total smoke production as low as 92.44 kW m-2 and 0.1 m2, respectively), which is the outstanding interpenetrated multinetwork hybrid aerogel that has achieved synergistic improvement in heat and fire insulation and mechanical performance. Therefore, the interpenetrated multinetwork hybrid aerogels are promising candidates for efficient heat insulation, fire prevention, and mechanically robust applications.

Sustainable furfuryl alcohol-based flame retardants with regular spherical morphology: Endow polypropylene with excellent flame retardancy, smoke suppression, and mechanical properties

Preparation of polyolefins possessing superior flame retardant and mechanical properties has always been a hot research topic. Herein, a novel high-performance flame retardant was designed and prepared to address the dilemma between flame retardancy and mechanical properties. Through self-stabilized precipitation polymerization of furfuryl alcohol (FA) and maleic anhydride (Ma), followed by successive amination and phosphorylation treatment, bio-based phosphorylated FMa microspheres (P-FMa) were successfully obtained. Benefiting from strong synergistic effect between P-FMa and ammonium polyphosphate (APP), the polypropylene (PP)/APP/P-FMa composites exhibited excellent flame retardant and smoke suppression properties. At a dosage of only 19 wt% APP/P-FMa, the PP/APP/P-FMa reached UL-94 V-0 rating and a limiting oxygen index of 32.2 %, and the peak heat release rate and peak smoke production rate decreased by 76.1 % and 52.6 % compared with neat PP, respectively, due to the formation of denser and firmer char layer. Notably, the tensile strength of PP/APP/P-FMa maintained at a high level of 43.2 MPa. More importantly, the impact strength reached 10.5 kJ/m2, increase by 138.6 % compared to PP/APP, mainly attributed to improved dispersion and compatibility between APP/P-FMa and PP matrix. Owing to its ability to simultaneously improve flame retardant and mechanical properties, P-FMa possesses great potiential as a high-performance flame-retardant filler.

Sodium lignosulfonate improve the flame retardancy of carboxymethyl chitosan @ melamine polyphosphate‐containing silicone acrylic emulsion‐based coatings

AbstractTo address the flammability concerns of silicone acrylate emulsion (SAE), it is of utmost importance to develop composite coatings that excel in flame retardancy and smoke suppression. In this research, we have utilized carboxymethyl chitosan (CMCS) bonded‐melamine polyphosphate (MPP)/sodium lignosulfonate (LS) to create SAE composite SiPC coatings through the sol–gel method for flame‐retarding plywood. The results obtained that CMCS pretreatment of MPP (CMPP) facilitates the filling of P‐containing components in the SAE composite SiPC coating to further form a continuous and dense cross‐linked structure. Appropriate dosage of LS (2 wt.%) improve the flame retardancy of the coatings, which is manifested the peak heat release rate drops from 237.4 to 142.4 kW m−2, total smoke production (TSP) is also significantly reduces by 55%. Notably, the coating undergoes a transformation into a nonflammable vitreous polyphosphate barrier layer while burning, effectively preventing the transfer of heat or mass. According to the calculation results of adsorption kinetics, the formaldehyde adsorption rate of the SiPC coating increased by 76.6%. Furthermore, the pyrolysis kinetics identify that the 3D Z.‐L.‐T model governs the coatings' pyrolysis, and the appropriate LS makes the pyrolysis Eα rise from 300.98 to 326.50 kJ mol−1 at 358 – 439°C, indicating enhanced thermal stability. In conclusion, our research has introduced a novel design strategy for developing the SiPC coating with exceptional properties, studies the flame‐retardant mechanisms of SAE composite SiPC coating, promotes the advancement of sustainable urban building materials, and explores a green, clean, and low‐cost ecological technology approach.

Comparative analysis of the prevalence of smoking and consumption of nicotine-containing products and their risk factors among students of medical and technical universities of Saint Petersburg based on data from the PROTECT study

BACKGROUND: Taking into account the importance of quitting smoking of any nicotine-containing products by young people in various social groups, a comparative analysis of the prevalence of smoking tobacco and nicotine-containing products among students of medical and technical universities in St. Petersburg was carried out. AIM: To compare the prevalence and structure of consumption of tobacco and nicotine-containing products, as well as the smoking behavior of students at medical and technical universities. MATERIALS AND METHODS: A cross-sectional cross-sectional study of a random sample of student groups included 1,105 respondents. RESULTS: The prevalence of tobacco smoking among students at a technical university was 2 times higher than at a medical university (p 0.01). Cigarette smoking was also more often noted at the onset of smoking among engineering students and in their families (p 0.05). 17.2% of North-Western State Medical University named after I.I. Mechnikov students and 14.2% of Saint Petersburg Electrotechnical University “LETI” named after V.I. Ulyanov (Lenin) students consume nicotine-containing products. Men from the medical university smoke cigarettes significantly more often than women, or use nicotine-containing products, as well as a combination of both. No similar gender differences were found at the technical university. Female doctors used ES more often than women from a technical university at the beginning of smoking (p 0.05). Men at a medical university started using nicotine-containing products more often than women, considering them the least dangerous to health (p 0.05). The example of friends was the most common reason for starting smoking among respondents from both universities (43.9 and 30.8%, respectively). Common risk factors for smoking any product among students of North-Western State Medical University and LETI were boyfriend/girlfriend smoking, smoking among one’s immediate environment. Studying in senior years was a protective factor for girls at a medical university in comparison with students at a technical university (odds ratio 0.48). CONCLUSIONS: The data obtained on the lower prevalence of tobacco smoking among medical university students compared to technical students may indirectly indicate the latter’s insufficient knowledge about the harmful effects of tobacco smoking on the body. The high prevalence of nicotine-containing products consumption in universities of various fields of study and the lack of significant differences in the share of their consumers can also be interpreted as an underestimation of the health risks of new smoking products. This requires adjustments to educational programs in order to increase students’ awareness of the potential health hazards not only of smoking cigarettes, but also of using any nicotine-containing products.

Flame-retardant performance of a novel lignin-based rigid polyurethane foam prepared from pulping black liquor

To improve the flame retardancy of rigid polyurethane foam (RPUF), black liquor lignin-based rigid polyurethane foam (LRPUF) was prepared in this work through a one-step foaming method using lignin and inorganic salt in black liquor lignin as the structural modifier and the additive flame retardant, respectively. Effect of the addition of carbon dioxide treated black liquor lignin (CBL) on the structure and flame retardancy of LRPUF, as well as the flame flame-retardant mechanism of LRPUF, were investigated. The limiting oxygen index (LOI) test and cone calorimetric tests showed that compared to the RPUF, the LOI of LRPUF with 40 wt% CBL increased from 18.9 % to 21.3 %, and the peak heat release rate, total heat release, and total smoke production decreased by 19.5 %, 25.3 %, and 20.5 %, respectively, indicating that the addition of CBL improved the flame retardancy of LRPUF. The flame-retardant mechanism was investigated by analyzing the structure and components of the char residue. We found that a dense protective layer, consisted of char residue and a considerable amount of sodium sesquicarbonate on the surface of the char residue, was formed after combustion. This study provided a novel strategy for the resource utilization of black liquor lignin.

Porous liquids assisted in-situ generated Co-LDH@MOF heterostructure with abundant defects for flame retardant and mechanical enhancement in polyurea composites

Preventing aggregation and inducing homogeneous dispersion of flame retardant nanofillers is critical to enhance the fire safety and mechanical properties of nanocomposites. Although chemical modifications are commonly used to improve the filler’s compatibility with the polymer chain, such methods are often cumbersome and limited. Herein, porous liquids (PLs) with flame retardant function were constructed in which porous defect-Co-LDH@ZIF-67 (d-LDH@ZIF) heterostructure particles were converted into liquid materials by electrostatic interaction with a large-volume solvent. This is also the first report of PLs in the field of flame retardant. Specifically, the d-LDH@ZIF heterostructure was designed by defect engineering and in situ growth strategy to compensate for the low catalytic activity and specific surface area of Co-LDH, and to serve as a rigid porous framework for PLs. Numerous cobalt/oxygen vacancies and lattice defects in the d-LDH@ZIF heterostructure have also been proven to confer higher flame retardancy relative to Co-LDH. d-LDH@ZIF porous liquids (PLs-d-L@Z) presents favorable liquid characteristics and achieves a monodisperse state in the polyurea matrix. The limiting oxygen index of polyurea composites blended with 20 wt% PLs-d-L@Z (3 wt% d-LDH@ZIF content) can be increased to 24.2 % and pass the V-0 rating in the UL-94 test. Moreover, the peak of heat release rate, total heat release, and total smoke production are reduced by around 40.4, 27.0, and 39.9 %, respectively, compared to neat polyurea. Emphatically, the PLs-modified polyurea composites exhibit significantly improved mechanical and impact resistance properties, as well as favorable chemical resistance. This strategy of liquefying solid flame retardant fillers will open an avenue to the design of functional nanomaterials for fire safety and other potential applications.